The present invention relates to a bearing which is capable of receiving a radial load, axial loads in two directions, and a moment load. The bearing may be used in several applications, such as an industrial machine, a robot, a medical instrument, a semiconductor/liquid crystal manufacturing apparatus, an optical instrument, an opto-electronic instrument, and so on.
As such, the present invention also relates to a rolling bearing device to be utilized in the spindle of a machine tool or another general high-speed rotation machine.
The present invention further relates to a rolling bearing for a compressor pulley.
Conventionally, as a bearing which is capable of receiving a radial load, axial loads in two directions, and a moment load, there are known a cross roller bearing and a four-point contact ball bearing. In the conventional cross roller bearing, between an inner race 100 and an outer race 200, there is incorporated a cylindrical-shaped roller 300 (see FIG. 94). On the other hand, in the conventional four-point contact ball bearing, between an inner race 100 and an outer race 200, there is incorporated a ball 400 (see FIG. 95).
However, in the conventional cross roller bearing and four-point contact ball bearing, there are found the following problems to be solved.
(1) In the case of the cross roller bearing, since a rolling element is a cylindrical-shaped roller 300 and the rolling contact surface 301 of the roller 300 is line contacted with a raceway groove 500, there is produced large torque.
(2) In the case of the four-point contact ball bearing, because a rolling element is a ball, when the bearing receives a pure axial load or when an axial load is dominant over a radial load, the four-point contact ball bearing produces smaller torque than the cross roller bearing of the same size.
On the other hand, when a radial load is dominant over an axial load or when the bearing receives a pure radial load, each ball 400 is contacted with a raceway groove 500 at four points 401, 401, 401 and 401 and, therefore, there occurs large spin slippage between the ball 400 and raceway groove 500, which results in large torque.
As the bearing to be used in the high-speed rotation machine such as the machine tool spindle, there has been employed in the prior art an angular ball bearing or a four-point contact ball bearing, as shown in FIGS. 96 to 98, for its high speed and axial rigidity. Reference numeral 900 designates a rotation shaft.
In FIG. 96, the radial load is borne by two cylindrical roller bearings 600, and axial loads in the two directions are borne or the axial displacements are restricted by two angular ball bearings 700.
In FIG. 97, the four angular ball bearings 700 bear the radial loads together with one cylindrical roller bearing 600 while bearing the axial loads in the two direction or restricting the axial displacements.
In FIG. 98, the radial load is borne by the two cylindrical roller bearings 600 as in FIG. 96, but the axial loads in the two directions are borne or the axial displacements are restricted by one four-point ball bearing 800, as shown in FIG. 99.
In these Figures: reference numeral 801 designates an outer race; numeral 802 an inner race; numeral 803 a rolling element; and numeral 804 a retainer.
The prior arts thus far described have the following problem.
In the structures of FIGS. 96 and 97 using the angular ball bearing 700, this one angular ball bearing 700 can bear only the axial load in one direction. In order to bear the axial loads in the two directions, therefore, it is customary to employ two or more angular ball bearings 700 in combination.
However, the bearing to be used in the high-speed rotation machine such as the machine tool spindle is demanded to have a high precision and therefore has a high price. As the number of angular ball bearings 700 to be arranged becomes the larger, moreover, the axial size of the bearing device becomes the larger therefore, the bearing device and accordingly the entire system cannot be made compact to cause a problem that the cost rises for the entire device.
In the structure employing the four-point contact ball bearing shown in FIG. 98 and FIG. 99, moreover, the single bearing can bear the radial load, the axial loads in the two directions, and the moment load so that the single four-point ball bearing 800 can realize the functions of the two angular ball bearings. Therefore, this structure has merits of a compact size and a low cost. Where the radial load is dominant over the axial loads or where a pure radial load is borne, however, the individual balls 803 of the four-point contact ball bearing 800 make contacts at four points with the races 801 and 802. Therefore, the balls 803 spin largely to cause a problem that a small spin wear performance cannot be attained. This problem is made especially serious by the action of the centrifugal force, especially in the case of the machine tool rotating at a high speed.
In order to improve the spin wear performance even a little, moreover, the clearance between the bearings is usually set positive. As a result, the rigidity of the bearings is lowered to exert adverse effects on the rigidity of the entirety of the bearing system for supporting the rotation shaft.
The present invention aims at solving the above problems found in the conventional cross roller bearing and four-point contact ball bearing. Accordingly, it is an object of the invention to provide a rolling bearing which can control spin slippage between a rolling element and a raceway groove and can reduce rolling resistance to realize low torque, thereby being able to receive a radial load, axial loads in two directions, and a moment load.
In attaining the above object, according to the invention, there is provided a rolling bearing, wherein a plurality of rolling elements are incorporated between a pair of races, each of the two races has a raceway groove defined by two raceway surfaces each having a radius larger than the radius of each of the rolling elements, the outside diameter of each rolling element serving as the rolling contact surface thereof has a curvature in the axial direction of the rolling element as well, the mutually adjoining ones of the rolling elements are arranged in such a manner that they cross each other alternately, and the outside diameter of each rolling element is always contacted at two points with the raceway surfaces of one of the races as well as with the raceway surfaces of the other.
The above-mentioned object can also be achieved by a rolling bearing comprising:
a first race and a second race, each having at least one raceway surface; and
a plurality of rolling elements rotatably disposed between the first race and the second race, each of the rolling elements having a rolling contact peripheral surface defined by rotating a curved bus line about a rotation axis of the rolling element, the curved bus line having a predetermined curvature that is smaller than a radius of the at least one raceway surface,
wherein the rolling contact peripheral surface of each of the rolling elements always contacts one point on each of the at least one raceway surface of the first race and the at least one raceway surface of second race, and wherein mutually adjoining rolling elements are arranged in a circumferential direction of the rolling bearing such that their rotation axes alternately cross one another.
One embodiment of the rolling bearing according to the present invention, each of the rolling elements may include at least one flat surface.
Another embodiment of the rolling bearing according to the present invention, each of the rolling elements may include two mutually opposing and flat-surfaces
In the rolling bearing according to the present invention, it is advantageous that each of the rolling elements is a top and bottom cut-shaped ball which is formed by cutting upper and lower portions of a ball so as to define the two mutually opposing and flat-surfaces.
In the rolling bearing according to the present invention, it is advantageous that each of the rolling elements is a top or bottom cut-shaped ball.
In the rolling bearing according to the present invention, it is advantageous that the first race comprises a first and a second raceway surface.
In the rolling bearing according to the present invention, it is advantageous that the first race further comprises a fastener operable to secure the first and second raceway surfaces to one another.
In the rolling bearing according to the present invention, it is advantageous that the second race comprises a first and a second raceway surface.
In the rolling bearing according to the present invention, it is advantageous that the second race further comprises a fastener operable to secure the first and second raceway surfaces to one another.
In the rolling bearing according to the present invention, it is advantageous to further include a placement device into which the mutually adjoining rolling elements are incorporated in such a manner that their rotation axes alternately cross one another.
In the rolling bearing according to the present invention, it is advantageous that the placement device is a retainer having alternately formed two-hold portions.
In the rolling bearing according to the present invention, it is advantageous that the placement device is a plurality of separators each having a diameter smaller than a diameter of each of the rolling elements and also having two recess-shaped arc grooves at mutually opposing surfaces in a crossing manner.
In the rolling bearing according to the present invention, it is advantageous that the placement device is a retainer having a number of pockets into which a same number of the rolling elements are respectively inserted, wherein the pockets are alternatively disposed on a periphery portion of the retainer in a staggered manner and arranged in a predetermined interval in the circumferential direction thereof.
In the rolling bearing according to the present invention, it is advantageous that at least one of the at least one raceway surface and the plurality of rolling elements includes a stainless steel.
In the rolling bearing according to the present invention, it is advantageous that at least one of the at least one raceway surface and the plurality of rolling elements includes a ceramic material.
In the rolling bearing according to the present invention, it is advantageous that at least one of the at least one raceway surface and the plurality of rolling elements includes a resin material.
In the rolling bearing according to the present invention, it is advantageous that at least one of the at least one raceway surface and the plurality of rolling elements includes an anti-corrosive coating on a surface thereof.
In the rolling bearing according to the present invention, it is advantageous to further include sealing plates interposed between the first race and the second race.
In the rolling bearing according to the present invention, it is advantageous to further include a flange formed in at least one of the first race and the second race.
In the rolling bearing according to the present invention, it is advantageous to further include a lubricant-containing polymer member disposed in an internal space of the bearing.
In the rolling bearing according to the present invention, it is advantageous that an internal clearance of the bearing is set to a negative value.
Moreover, the object can also be attained by a rolling bearing for a compressor pulley comprising:
at least one bearing, the bearing including:
a first race and a second race, each having at least one raceway surface;and
a plurality of rolling elements rotatably disposed between the first race and the second race, each of the rolling elements having a rolling contact peripheral surface defined by rotating a curved bus line about a rotation axis of the rolling element, the curved bus line having a predetermined curvature that is smaller than a radius of the at least one raceway surface,
wherein the rolling contact peripheral surface of each of the rolling elements always contacts one point on each of the at least one raceway surface of the first race and the at least one raceway surface of second race, and wherein mutually adjoining rolling elements are arranged in a circumferential direction of the rolling bearing such that their rotation axes alternately cross one another.
In addition to this, the present invention has been conceived in view of the above-mentioned problems intrinsic to the prior arts, and has an object to provide a rolling bearing device which can spare the space and lower the cost and which is suited for high-speed rotations of a machine tool.
The object of the present invention can also be achieved by a rolling bearing device for supporting a rotation shaft by a bearing comprising:
at least one bearing, the bearing including:
a first race and a second race, each having at least one raceway surface; and
a plurality of rolling elements rotatably disposed between the first race and the second race, each of the rolling elements having a rolling contact peripheral surface defined by rotating a curved bus line about a rotation axis of the rolling element, the curved bus line having a predetermined curvature that is smaller than a radius of the at least one raceway surface, wherein the rolling contact peripheral surface of each of the rolling elements always contacts one point on each of the at least one raceway surface of the first race and the at least one raceway surface of second race, and wherein mutually adjoining rolling elements are arranged in a circumferential direction of the rolling bearing such that their rotation axes alternately cross one another.
Further, the present invention has been conceived in view of those problems of the prior art, and has an object to provide a rolling bearing for a compressor pulley, which has a high moment rigidity and an excellent spinning wear performance and which can make the bearing compact and lower the cost.
In order to achieve the above-specified object, according to the present invention, there is provided technical means: a rolling bearing for a compressor pulley, comprising: a pair of races having two raceway surfaces each having a larger radius of curvature than the rolling element radius; and a plurality of rolling elements, the outside diameter of which has a curvature, too, in the axial direction for rolling contact surfaces and which are alternately arranged in a crossing manner to contact with the raceway surfaces of one and the other races always having mutually opposing outside diameters, individually at one point and totally at two points, whereby one is used for the pulley of a cooler compressor of an automobile.
To achieve the objective, the present invention may provide, as technical means, a roller bearing comprising: a pair of races, each having a raceway groove defined by two raceway surfaces, said raceway groove having a diameter greater than the radius of a rolling element; a plurality of rolling elements to be incorporated between said pair of races; the outside diameter of each of said rolling elements, which diameter is to act also as a rolling contact surface, having curvature in an axial direction; continuous rolling elements being arranged such that the outside diameter of one rolling element crosses the outside diameter of another, adjacent rolling element with an angle therebetween; two points of contact always existing between the outside diameter of each of said rolling elements and said raceway surface of one race and said raceway surface of the other race; and sealing plates which are interposed between the pair of races.
Further, the present invention may provide a roller bearing comprising: a pair of races, each having a raceway groove defined by two raceway surfaces, said raceway groove having a diameter greater than the radius of a rolling element; a plurality of rolling elements to be incorporated between said pair of races; the outside diameter of each of said rolling elements, which diameter is to act also as a rolling contact surface, having curvature in an axial direction; continuous rolling elements being arranged such that the outside diameter of one rolling element crosses the outside diameter of another, adjacent rolling element with an angle therebetween; two points of contact always existing between the outside diameter of each of said rolling elements and said raceway surface of one race and said raceway surface of the other race; and a flange which is formed in either or both of the pair of races.
The present invention may also provide a roller bearing comprising: a pair of races, each having a raceway groove defined by two raceway surfaces, said raceway groove having a diameter greater than the radius of a rolling element; a plurality of rolling elements to be incorporated between said pair of races; the outside diameter of each of said rolling elements, which diameter is to act also as a rolling contact surface, having curvature in an axial direction; continuous rolling elements being arranged such that the outside diameter of one rolling element crosses the outside diameter of another, adjacent rolling element with an angle therebetween; two points of contact always existing between the outside diameter of each of said rolling elements and said raceway surface of one race and said raceway surface of the other race; and the internal space of the bearing which is filled with a lubricant-containing polymer member.
To achieve the object, the present invention provides, as technical means, a roller bearing comprising: a pair of races, each having a raceway groove defined by two raceway surfaces, said raceway groove having a diameter greater than the radius of a rolling element; a plurality of rolling elements to be incorporated between said pair of races; the outside diameter of each of said rolling elements, which diameter is to act also as a rolling contact surface, having curvature in an axial direction; continuous rolling elements being arranged such that the outside diameter of one rolling element crosses the outside diameter of another, adjacent rolling element with an angle therebetween; two points of contact always existing between the outside diameter of each of said rolling elements and said raceway surface of one race and said raceway surface of the other race; and internal clearance of said bearing being set to a negative value by means of application of pre-load.
To the end, according to the invention, there is provided a rolling bearing comprising a plurality of rolling elements built in between a pair of races, each of the races having a raceway groove having a raceway surface having a larger radius than the radius of the rolling element and at least one of the races consisting of two raceway surfaces, wherein each of the rolling elements has an outer shape like a ball with one side cut, the outer diameter of each of the rolling elements as a rolling contact surface also has a curvature in an axial direction, the rolling elements are placed like a cross alternately on the circumference of a circle, and the outer diameter of each of the rolling elements is in contact with one point on the raceway surface of one race and one point on the raceway surface of the other race, the races always facing each other.
To the end, according to the invention, there is provided a rolling bearing comprising a plurality of rolling elements built in between a pair of races, each of the races having a raceway groove having a raceway surface having a larger radius than the radius of the rolling element and at least one of the races consisting of two raceway surfaces, wherein the outer diameter of each of the rolling elements as a rolling contact surface also has a curvature in an axial direction and the rolling elements are placed like a cross alternately on the circumference of a circle and wherein the outer diameter of each of the rolling elements is in contact with one point on the raceway surface of one race and one point on the raceway surface of the other race, the races always facing each other, wherein the invention is characterized by the fact that the following configuration is adopted:
Stainless steel, ceramics, resin, or the like is used as the material of all or at least one of the three elements of the inner and outer races making up one pair of races and the rolling elements, or anticorrosive coating treatment is executed on the surface of at least one of the three elements of the inner race, the outer race, and the rolling elements of the bearing depending on the use environment.
The present invention has been conceived in view of those problems intrinsic to the prior arts. It is another object to provide a rolling bearing device which can spare the space and lower the cost and which is suited for high-speed rotations of a machine tool.
In order to achieve the above-specified object, according to technical means of the present invention, there is provided a rolling bearing device for supporting a rotation shaft by a bearing, characterized: by comprising at least one rolling bearing including a plurality of rolling elements incorporated between a pair of races; in that each of said races has a raceway groove composed of raceway surfaces of a larger radius than that of the rolling elements; in that at least one of said races is composed of two raceway surfaces; in that said rolling elements are given a curvature in the axial direction at each their outside diameter for a rolling contact surface and are arranged alternately to cross each other on the circumference; and in that the outside diameter of each rolling element makes a totally two contacts with the raceway surface of one of the mutually opposing races and the raceway surface of the other mutually opposing race.
Moreover, there is provided a rolling bearing device in which the rotation shaft is supported by one rolling bearing having the above-specified construction and two cylindrical roller bearings.
Moreover, there is provided a rolling bearing device in which the rotation shaft is supported by two rolling bearings having the above-specified construction and one cylindrical roller bearings.
To the end, according to the invention, there is provided a rolling bearing comprising a plurality of rolling elements built in between a pair of races, each of the races having a raceway groove having a raceway surface having a larger radius than the radius of the rolling clement and at least one of the races consisting of two raceway surfaces, wherein each of the rolling elements has an outer shape like a ball with one side cut, the outer diameter of each of the rolling elements as a rolling contact surface also has a curvature in an axial direction, the rolling elements are placed like a cross alternately on the circumference of a circle, and the outer diameter of each of the rolling elements is in contact with one point on the raceway surface of one race and one point on the raceway surface of the other race, the races always facing each other.